PubMed Health⌕ Search

Biomedical subjects

P Fey

Publications and source records attributed to P Fey.

16 recordsLinked to original sources
PubMed2005

The genome of the social amoeba Dictyostelium discoideum.

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.

ATP-Binding Cassette Transporters↗
PubMed2001

Molecular motors and membrane traffic in Dictyostelium.

Phagocytosis and membrane traffic in general are largely dependent on the cytoskeleton and their associated molecular motors. The myosin family of motors, especially the unconventional myosins, interact with the actin cortex to facilitate the internalization of external materials during the early steps of phagocytosis. Members of the kinesin and dynein motor families, which mediate transport along microtubules (MTs), facilitate the intracellular processing of the internalized materials and the movement of membrane. Recent studies indicate that some unconventional myosins are also involved in membrane transport, and that the MT- and actin-dependent transport systems might interact with each other. Studies in Dictyostelium have led to the discovery of many motors involved in critical steps of phagocytosis and membrane transport. With the ease of genetic and biochemical approaches, the established functional analysis to test phagocytosis and vesicle transport, and the effort of the Dictyostelium cDNA and Genome Projects, Dictyostelium will continue to be a superb model system to study phagocytosis in particular and cytoskeleton and motors in general.

Actins↗
PubMed2000

[Narcolepsy. An illness in transition].

The signs of narcolepsy have been known since the last century and the tetrad of symptoms was described 50 years ago: excessive sleepiness, cataplexy, sleep paralysis, and hallucinations. Polysomnography typically shows decreased sleep and REM sleep latency, and laboratory testing reveals a high association with the human leucocyte antigens (HLA) DQB1*0602 and DQA1*102. Actual studies suggest disturbances in the orexin (hypocretin) neurotransmitter system. However, the exact pathophysiology is still unclear. In Germany, about 1500 patients diagnosed with narcolepsy are known. The prevalence in Caucasian populations is estimated at 50/100,000. Thus, the number of undiagnosed patients is likely to be high.

Cross-Sectional Studies↗
PubMed1999

Cortexillin I is required for development in Polysphondylium.

The actin binding proteins cortexillin I and II play a major role in Dictyostelium cytokinesis, in which they are found localized to the membranes of the cleavage furrow. Here we report on cortexillin I mutants isolated by gene trapping in Polysphondylium. The original mutation and reconstructed versions of the original, as well as cortexillin I deletions, are unable to form aggregation streams under starvation conditions. The fruiting bodies that do form when cells are grown on bacterial lawns lack the one- and two-dimensional symmetries so apparent in wild type. These two phenotypes and the proposed structural basis for them suggest that cortexillin I functions in chemotaxis and morphogenesis in addition to its role in cytokinesis.

Amino Acid Sequence↗
PubMed1999

Expression of prestalk and prespore proteins in minute, two-dimensional Dictyostelium slugs.

We show that exceedingly small two-dimensional slugs of Dictyostelium differentiate normally and have an anterior prestalk zone and a posterior prespore zone. Using GFP as a marker attached to the appropriate promoter, prestalk expression is concentrated in the anterior, while prespore expression is produced in the posterior, closely resembling what is found in normal, large slugs.

Animals↗
PubMed1997

Gene trapping with GFP: the isolation of developmental mutants in the slime mold Polysphondylium.

In order to study how a cell mass undergoes a transition from one symmetry to another in the slime mold Polysphondylium, we developed a genetic screen in which mutant phenotype and gene expression can easily be visualized in the living organism. The screen combines restriction enzyme-mediated integration (REMI) [1,2] and green fluorescent protein (GFP) [3] expression. In REMI, a restriction enzyme is electroporated along with linearized vector into cells, thus determining the site of plasmid insertion and often increasing the integration frequency. A set of transforming plasmids carrying the GFP coding sequence in three reading frames was used for transformation. The plasmids were constructed so that GFP could be expressed only under control of a host promoter. Living transformants expressing GFP spatially and temporally could be rapidly identified in a very large background of non-expressing cells and fruiting bodies. The phenotypes of representative mutants range from cells that cannot aggregate and initiate cell-cell interactions, through mutant fruiting bodies, to apparently wild-type fruiting bodies expressing GFP in all or a subpopulation of cells. The ability to screen mutant living cells and tissues for GFP expression is rapid and effective and likely to have application in many transformable systems where screening by gene and promoter trapping is essential for understanding temporal and spatial gene regulation.

Cloning, Molecular↗
PubMed1997

Metabolism of cerivastatin by human liver microsomes in vitro. Characterization of primary metabolic pathways and of cytochrome P450 isozymes involved.

Biotransformation of cerivastatin, a new cholesterol-lowering drug, by human liver microsomes was investigated using the 14C-labeled drug. Metabolite profiles were established by HPLC and structures of metabolites were elucidated. Two metabolic pathways were equally important, demethylation of the benzylic methyl other and hydroxylation at one methyl group of the 6-isopropyl substituent. The product of combined hydroxylation and demethylation was observed as a minor metabolite. During sample preparation the lactone forms of both primary metabolites were isolated in small amounts. Detailed structural analysis by NMR and LC-ESI-MS showed that hydroxylation occurred with high regio- and stereoselectivity. The proposed structures were confirmed by chemical synthesis of enantiomerically pure reference compounds. Microsomes from a human lymphoblastoid AHH-1 cell line, stably expressing CYP 3A4, catalyzed the demethylation reaction. Upon incubation of cerivastatin with human liver microsomes in the presence of the specific CYP 3A inhibitor TAO, both hydroxylation and demethylation were considerably reduced. This indicates that CYP 3A enzymes play a major role in cerivastatin metabolism.

Anticholesteremic Agents↗
PubMed1997

Long-term blockade of the angiotensin II receptor in renin transgenic rats, salt-loaded Dahl rats, and stroke-prone spontaneously hypertensive rats.

These studies were designed to investigate the protective effects of the new angiotensin II receptors antagonist BAY 10-6734 (6-n-butyl-4-methoxycarbonyl-2-oxo-1[(2'-(1H-tetrazol-5-yl) -3-fluorobiphenyl-4-yl)methyl] 1,2-dihydropyridine, CAS 156001-18-2) on haemodynamic, hormonal, renal, and structural parameters in renin transgenic rats (TGR(mRen2)27), salt-loaded Dahl S and R rats, and salt-loaded stroke-prone spontaneously hypertensive rats (SHR-SP) in long-term trials. Study 1: In SHR-SP the development of blood pressure, cardiac hypertrophy, and the deleterious effects of salt loading on kidney structure and kidney function was prevented by BAY 10-6734. Study 2: In salt-loaded Dahl S rats with a suppressed plasma renin activity treatment with BAY 10-6734 did not delay the increase in blood pressure but prevented cardiac hypertrophy and the increase in plasma ANP (Atrial natriuretic peptide). Study 3: TGR develop malignant hypertension associated with cardiac hypertrophy, elevated left-ventricular end-diastolic pressure and increased plasma ANP. After 6 weeks of treatment with BAY 10-6734 (30 mg/kg p.o. bid) cardiac pump function was improved and cardiac hypertrophy was reversed in this angiotension dependent form of hypertension. The beneficial effects of BAY 10-6734 in these different animal hypertension models are also emphasized by a reduction in mortality.

Aldosterone↗
PubMed1995

Green fluorescent protein production in the cellular slime molds Polysphondylium pallidum and Dictyostelium discoideum.

The green fluorescent protein-encoding gene from Aequorea victoria has been cloned into several different transforming vectors and expressed in the cellular slime molds, Polysphondylium pallidum and Dictyostelium discoideum. We find that the protein is stable and non-toxic in both species, can be easily visualized in living and fixed specimens, and can be used to purify rare cells by fluorescence-activated cell sorting (FACS).

Animals↗
PubMed1995

Development in one dimension: the rapid differentiation of Dictyostelium discoideum in glass capillaries.

When Dictyostelium discoideum cells are drawn into a fine glass capillary, they rapidly begin the first steps toward the formation of prestalk and prespore zones. Some of the events occur within a minute or two, whereas others follow later. The cells in the front segment are actively motile and those in the hind segment are passive. The volumes of the segments are proportional for different-sized cell masses, and those proportions are the same as those found in normal slugs. When the cells are stained with the vital dye neutral red, the anterior zone becomes darker simultaneously with the formation of the division line. Green fluorescent protein expressed from a stalk-specific promoter is synthesized mostly in the anterior end. Later, this capillary prestalk zone shows a sharp increase in alkaline phosphatase activity, which is known to be characteristic of prestalk cells.

Alkaline Phosphatase↗
PubMed1994

Molecular cloning, expression, and chromosomal localization of two isoforms of the AE3 anion exchanger from human heart.

Cl-/HCO3- exchange contributes to regulation of pHi and [Cl-] in cardiac muscle, with possible effects on excitability and contractility. We have isolated human heart cDNAs, which encode two isoforms of the anion exchanger AE3. These clones share long portions of common sequence but have different 5' ends encoding distinct amino-terminal amino acid sequences. The longer AE3 polypeptide of 1232 amino acids, bAE3, displays nearly 96% amino acid sequence identity to the rat and mouse AE3 "brain isoforms." The shorter cAE3 polypeptide of 1034 amino acids in length corresponds to the rat AE3 "cardiac isoform." The unique N-terminal 73 amino acids of the cAE3 sequence are less well conserved between rat and human. Northern blot analysis with isoform-specific probes revealed the presence of both cAE3 and bAE3 mRNAs in human heart tissue. Both AE3 protein isoforms were overexpressed in Chinese hamster ovary cells and detected by immunoblot with antipeptide antibodies. Immunoblot studies of human cardiac membranes detected only cAE3 polypeptides, which were apparently not susceptible to enzymatic deglycosylation. Injection into Xenopus oocytes of cRNAs encoding either cAE3 or bAE3 produced increased 36Cl- uptake into the oocytes, confirming the ability of both AE3 isoforms to transport Cl-. The human AE3 gene was localized to chromosome 2. AE3 may provide a new pharmacologic target for antiarrhythmic and cardioprotective drugs.

Amino Acid Sequence↗
PubMed1993

Hair analysis as evidence in forensic cases.

Because hair analysis can be used for the determination of drug use months after drug consumption, hair analysis data can often act as important and even decisive evidence in the courtroom. More recently developed GC/MS methods offer excellent sensitivity and can make the distinction between chronic heroin and codeine use, which was not possible earlier with radioimmunoassay techniques. From more than a thousand hair analyses, the morphine/codeine ratios necessary to determine heroin use were set at 5:1 for low morphine concentrations (< 1 ng/mg hair) and 2:1 for concentrations above 1 ng/mg hair. The distinction can be further focused with the additional analysis of the metabolite monoacetylmorphine (MAM). As can be seen from several case examples, hair analysis cannot pinpoint an exact date of opiate use, but it can be used to validate or invalidate a subject's statement concerning his/her drug consumption. Interpretations should always be made cautiously. Ranges, means and medians are also listed for amphetamine, cocaine and cannabis and work is under way to draw similar safety guidelines for these drugs.

Codeine↗
PubMed1993

Simultaneous determination of drugs of abuse (opiates, cocaine and amphetamine) in human hair by GC/MS and its application to a methadone treatment program.

A new method was developed for the simultaneous detection and quantitation of 6-acetyl-morphine (MAM), amphetamine, benzoylecgonine (BZE), cocaine, codeine, dihydrocodeine, EDDP (methadone metabolite), methadone and morphine in hair. The hair samples were washed, cut into 2-cm segments, pulverized, incubated with phosphate buffer and beta-glucuronidase/aryl-sulfatase. After solid phase extraction and derivatization with pentafluoropropionic anhydride/pentafluoropropanol, the drugs were identified and measured by gas chromatography/mass spectrometry using their deuterated analogues as internal standards. The method is reproducible with detection limits under 0.1 ng/mg hair for almost all substances tested. Fifteen hair samples from five subjects of a methadone treatment program were collected in a 6-month period. The hair samples were segmented and examined for methadone, its main metabolite EDDP, and drugs of abuse. Of the 96 segments analysed, 95% were positive for methadone (mean value, 10.9 ng/mg), 76% for the metabolite EDDP (mean value, 1.2 ng/mg), 69% for opiates (mean values, MAM, 7.3 ng/mg; morphine, 2.9 ng/mg; codeine, 1.0 ng/mg) and 43% for cocaine (mean values, cocaine, 2.6 ng/mg; BZE, 1.1 ng/mg). A correlation of 0.63 was found between administered methadone dosages and concentrations measured by hair analysis. Further investigation is needed to clarify interindividual differences.

Adult↗
PubMed1992

Human peripheral blood gamma delta T cells respond to antigens of Plasmodium falciparum.

Peripheral blood lymphocytes from donors previously unexposed to malaria parasites proliferate in vitro when stimulated with whole parasitized red blood cells of several different strains of Plasmodium falciparum. Here we show that both cells enriched for both memory (CD45R0+) and naïve (CD45R0-) phenotype can respond. Cells involved in these responses occur at frequencies similar to those observed for recall antigens such as tetanus toxoid but at lower frequencies than observed for the superantigens staphylococcal enterotoxin B or the mitogenic lectin phytohemagglutinin (PHA). Proliferation is inhibited by antibodies to class II MHC and to CD3 molecules. Stimulation of purified CD45R0- T cells by whole parasitized red blood cells for 6 days results in the generation of a large proportion of gamma delta T cell blasts of V gamma 9V delta 2 TCR phenotype and in the acquisition of the CD45R0 molecule within the blast cell population. The rapid generation of a vigorous primary in vitro gamma delta T cell response by malarial parasites may reflect the situation during primary malarial infection.

Animals↗
PubMedDate not supplied

Identification and quantitation of cocaine and its metabolites, benzoylecgonine and ecgonine methyl ester, in hair of Bolivian coca chewers by gas chromatography/mass spectrometry.

Twenty hair samples obtained from Bolivian mine workers who chewed 3-8 g of coca leaves daily for several years were analyzed for cocaine and its main metabolites, benzoylecgonine (BZE) and ecgonine methyl ester (EME). A new method was developed for the detection and quantitation of cocaine and its metabolites, BZE and EME, from hair in a single procedure. The hair samples were washed, cut into 56 segments (2-cm length), pulverized, and incubated with phosphate buffer and the enzyme beta-glucuronidase-arylsulfatase. After solid phase extraction and derivatization with pentafluoropropionic anhydride/pentafluoropropanol, the drugs were identified and measured by gas chromatography/mass spectrometry (GC/MS) using deuterated cocaine, BZE, and EME as internal standards. The method is reproducible (cocaine, CV = 8%; BZE, CV = 14%) and the detection limit for cocaine and BZE was 0.1 ng/mg, for EME 1 ng/mg. In the different hair segments, cocaine was found to be present in concentrations between 1.4 to 50.6 ng/mg, benzoylecgonine from 0.4 to 17.6 ng/mg, and ecgonine methyl ester traces below the calibration curve of approximately 12.9 ng/mg. In 95% of the cases cocaine exceeded BZE and EME in concentration.

Adolescent↗